The roof support structure of a commercial or industrial type building is typically constructed of parallel, spaced apart joists or purlins over which are supported the various component elements comprising the roof. Fabrication and constructions of such roofs vary widely and are exemplified by the disclosures of numerous U.S. patents. Several decades ago, the only essential purpose of a roof on most buildings was to protect and enclose the interior spacing against direct exposure to the weather elements. With the advent of temperature controlled space, particularly air conditioning as now known, and energy conservation associated with increased costs of heating fuel, the use of thermal insulation associated with the roof structure has become increasingly important. Not only does the use of thermal insulation provide a greater comfort factor within the conditioned space, but it also serves to reduce fuel consumption along with capital cost and operating cost of the conditioning equipment.
Insofar as various roof insulation systems have been disclosed in the patent literature, they generally differ from each other in the specific features of construction, method of application, useful longevity, finished appearance, ultimate degree of effectiveness for the intended purpose and/or cost of fabrication. It is known, for example, to support thermal insulation from the underside of the purlins as disclosed for example in U.S. Pat. No. 4,069,636. Such systems were specifically intended for a retrofit situation and frequently encounter obstructions such as light fixtures and sprinkler systems which interfere with installation tending to increase the unit cost over what could otherwise be achieved. Where the under joist type installations have utilized prefabricated components they are frequently dependent on critical dimensional relationships in order to effect ultimate assembly and support of the installed insulation. Since joist or purlin spans or spacings are subject to dimensional variations, dependence on a fixed dimension interlock cannot only create installation havoc but also can incur considerably difficulty as the purlins tend to roll through temperature induced expansion and contraction.
By and large the economics of roof insulation, particularly in a retrofit situation for industrial buildings, favor placement of the insulation material whether of a radiant barrier type, blanket type or a combination thereof between purlins near and below the roof deck. Such retrofit environments may even include prior insulation that is to be supplemented for enhancing the thermal barrier thereat whereby reduced heat gain in summer and reduced heat loss in winter can be achieved. Most important in connection with these add-to installations is that they are frequently contracted for on competitive bid basis. To compete effectively therefor, it is essential that labor costs for installation be minimized to the maximum extent possible while maintaining the quality of workmanship and materials intended to be provided. The difficulties and complexities of such installations should be readily apparent yet despite recognition of the foregoing problems, a ready solution therefore has not heretofore been known.